The notion of stability is central to the definition of personality traits, which are generally thought of as enduring tendencies or habitual patterns of behavior, thoughts, and emotions (McCrae & Costa, 2003), but stability does not imply immutability. Under normal circumstances, adult traits are largely stable, as indicated by high correlation coefficients computed for a group assessed twice on the same trait. These coefficients represent the average stability for a sample, but individuals vary in terms of their intra-individual stability. Despite the relative stability of individual differences, in recent years we have extended the studies of mean-level change in personality by examining longitudinal trajectories in more diverse samples and cross-sectional trends across cultures. Furthermore, we aim to delineate the neural and cognitive correlates of personality dimensions across longitudinal assessments. Most recently, we have begun investigating the association between personality traits and decision making. We recently investigated the personality correlates of risky decision making in healthy older adults. We also continue to collect fMRI studies of brain activation during decision making and will relate personality variables to patterns of brain activation during gains and losses, as well as in relation to individual differences in risk preference.